The seesaw battle between Libyan insurgents and Moammar Khadafy’s army intensified yesterday along the Mediterranean coastline, where a rebel push toward the capital was challenged by helicopter gunships.

The protesters-turned-rebels — backed by mutinous army units and armed with weapons seized from storehouses — are going on the offensive to try to topple Khadafy’s 41-year-old regime.

Pro-Khadafy forces have responded with counteroffensives to try to retake the oil port of Brega and the rebel-held city of Zawiya, west of Tripoli, where bloody street battles were reported over the weekend.

The insurgents, inspired by the success of demonstrators in Egypt, have clashed with Khadafy’s forces, pushing Libya toward civil war and making the North African nation the scene of the bloodiest episode in the Arab world’s pro-democracy push.

The United States, which has called for Khadafy to step down, backed its demand with some military muscle, with naval forces moving closer to Libya’s shores.

Washington also has secretly asked the Saudis to send weapons to the Libyan rebels on America’s behalf, but the request has not been granted, according to the UK newspaper The Independent.

The move could ease the pressure on the United States to establish a no-fly zone over Libya to prevent Khadafy from using his warplanes to attack the population, the paper said. The Obama administration has instead relied on tough talk and sanctions imposed by the United Nations.

“Lots of people throw around phrases like ‘no-fly zone,’ ” William Daley, the new White House chief of staff, said on NBC’s “Meet the Press.” “They talk about it as though it’s just a video game.”

Despite the Obama administration’s caution, three senators, from both sides of the political aisle, called on the United State to police Libyan airspace.

Sen. John Kerry (D-Mass.) joined Sens. John McCain (R-Ariz.) and Mitch McConnell (R-Ky.) in urging US forces to carve out a no-fly zone.

“We can’t risk allowing Khadafy to massacre his own people from the air,” McCain said on ABC’s “This Week with Christiane Amanpour.”

In the city of Misrata, 120 miles east of Tripoli, 20 people were killed and 100 wounded yesterday. Residents said pro-Khadafy forces punched into the city with mortars and tanks but were pushed out five hours later by rebel forces.

Abdel Fatah al-Misrati, a rebel leader, said Khadafy’s soldiers didn’t know what hit them. Commanders intentionally cleared a path for government tanks to enter the city, then surrounded them and attacked with anti-aircraft guns and mortars, he said.

“Our spirits are high,” Fatah al-Misrati added. “The regime is struggling, and what is happening is a desperate attempt to survive and crush the opposition. But the rebels are in control of the city.”